Production of desulfurized liquids and gases from coal

ABSTRACT

An integrated process for simultaneously recovering liquid and gaseous products from coal. A slurry is formed from crushed coal and recycled oil and is introduced to a three-zone reactor along with a hydrocracking catalyst and sand, the latter of which acts as a conveying medium. In the first zone, coal liquids are extracted and conveyed to a fractionation unit. In the second zone, the carbon coked on the solids is gasified with air creating a producer gas which flows upwardly countercurrent to the downward flow of the aforementioned mixture and supplying heat for the extraction stage. In the third stage, the remaining carbon is gasified with oxygen and carbon dioxide to a substantially nitrogen-free carbon monoxide. The carbon monoxide is desulfurized in a metal oxide bed.

United States Patent [191 Leas et al.

[4 1 Dec. 18, 1973 PRODUCTION OF DESULFURIZED LIQUIDS AND GASES FROMCOAL Primary ExaminerDelbert E. Gantz Assistant Examiner-J. W. HellwegeAttorney,lohn J. Byrne AB C [73] Assignee: Leas Brothers Development I vT C rp ati C l bi Ci l d An integrated process for simultaneouslyrecovering liquid and gaseous products from coal. A slurry is [22] 1972formed from crushed coal and recycled oil and is in- [21] App]. No;236,643 troduced to a three-zone reactor along with a hydrocrackingcatalyst and sand, the latter of which acts as a conveying medium. Inthe first zone, coal liquids are [52] Cl 208/ i extracted and conveyedto a fractionation unit. In the 5 l 1 Cl I 3 second zone, the carboncoked on the solids is gasified d l g G with air creating a producer gaswhich flows upwardly l e o arc /5 241 23 countercurrent to the downwardflow of the aforementioned mixture and supplying heat for the extractionstage. In the third stage, the remaining carbon is [56] References C'tedgasified with oxy en and carbon dioxide to a substang UNITED STATESPATENTS tially nitrogen-free carbon monoxide. The carbon 3,088,8165/1963 Huntington 48/63 monoxide is desulfurized in a metal oxide bed.3,l07,985 10/1963 Huntington 208/10 3,440,162 4/1999 Lawson 201/23 6Clam, 1 Drawmg Figure 40 CATALYST- MAKE-UP sANo-46 SAND HVDROCRACKING23: CATALYST. 42 RAW 1 I CZlIJJZI-IFD 7/ R 2 DESULFURIZED i 4' EMOVALGAS 85 /2 SYSTEM snsoums M69 FEED ABSORBER -1 H23 L25: liarx GASOLINE89\ CLAUS i L 77 UNIT s t L'lGHT /6'\ 1 "11$?" mEsEL FUEL N2 iiHEAVYGOAL DIESEL FUEL SLgIIlRV CYCLE H2 w I i cicLz MIX TANK AND GASSES 78:56 :7 HEAVY OIL-T018 2 36 g 80 .9/\ N2 FOR 9a #66 I20 DRYING COAL-O|L 25 92 a 428 I40 /3\6 L EWCTOR SLURRV ASH COBALT AIR COBALT i REMOVAL 1pDES. %2?" oxveen HEAVY I go 84 UNIT STORAGE V GENERATOR FROM 72 HGENERATOR 755 3a SAND Lock 2 3 N5 SEPARATOR PRODUCTION OF DESULFIJRIZEDLIQUIDS AND GASES FROM COAL This invention-relates to a process forsimultaneously recovering liquid and gaseous products from raw coal.

It is desirable from an economic'standpoint to use coal to produce bothliquid and gaseous fuels since coal is relatively inexpensive comparedto petroleum crude oil and is quite abundant in contrast to our rapidlydwindling domestic supply of petroleum and natural gas resources.However, the prior art apparatus for recovering liquids and gases fromcoal is quite complicated and inefficient, placing the operation costthereof out of proportion such that the production of fuels from coal isnot commensurate with the costs involved. Another drawback to using coalas the source of fuel is the substantial pollutants it containsprimarily in the form of sulfur, requiring the end products to bedesulfurized prior to consumption.

It is an objective of this invention to provide a relatively simple andeconomically feasible process for simultaneously recovering liquid andgaseous fuels from coal.

It is a further objective of this invention to provide means fordesulfurizing the liquid and gaseous products recovered from coal priorto consumption thereof.

It is a further objective of this invention to provide an integratedprocess wherein the liquid and gaseous products are simultaneouslyrecovered from the coal in a single reactor tower. The tower is dividedinto a plurality of zones for various stages of separation therebyeliminating the need for costly, inefficient transfer apparatus as isrequired when separate reactors are used for the individual stages ofseparation.

It is a further objective of this invention to provide an integratedprocess for recovering liquid and gaseous fuels from coal wherein thecatalyst used in the hydrocracking stage is continuously regenerated andrecycled for further use.

It is a further objective of this invention to utilize sand,metallurgical slag or the like as a conveying medium. The sand is mixedwith the coal and catalyst and assists in propelling the coal particlesdownwardly through the vertically stacked zones in the reactor tower.The particular feature is related to the process described in U.S. Pat.No. 3,617,464, dated Nov. 2, 1971, entitled COAL EXTRACTION METHOD ANDAPPARATUS.

It is a further objective of this invention to provide an integratedprocess including various separation zonesv in a single reactor towerwherein the heat from one zone can be utilized in an adjacent zone. Thegases produced in lower zones heat the solids in the upper zones bydirect gas-solid contact.

More particularly, raw, crushed coal is fed to a lockbin, feeder and isdried by the injection of hot nitrogen or other suitable drying gas. Thecoal is then mixed with a solvent such as a tetralin-decalin solution orre cycle oil and the slurry is fed to the top of the reactor tower atwhich point it is mixed with sand, metallurgical slag or the like and ahydrocracking catalyst such as cobalt, tungsten, molybdenum or iron. Thereactor tower is divided into three zones for various stages ofoperation. In the top zone, the coal liquids are extracted and arehydrocracked with hydrogen and other gases introduced to the bottom ofthe zone. The extracted liquids are then conveyed to a fractionationunit. The extracted, residual heavy hydrocarbons are coked. Heat forthis zone is supplied from a second or middle zone wherein the coke,sand and other carbonaceous materials are gasifled by the injectionofheated air resulting in heated producer gas which is passed upwardlythrough the middle zone and through the first zone and is taken off thetop of the reactor and conveyed to the fractionation unit. Also in thesecond zone the fly ash is fluidized and separated out for removal fromthe reactor tower. The solids continue to flow downwardly to a third orbottom zone wherein any remaining carbon is gasifled with oxygen andcarbon dioxide to produce a substantially nitrogen-free carbon monoxide.The carbon monoxide is taken off and desulfurized in a metal oxide bed,preferably cobalt oxide and the resultant desulfurized carbon monoxideis con veyed to a distribution points and used to produce hydrogen forthe first zone and carbon monoxide for the bottom zone. A second cobaltoxide bed is provided for the vacuum recovery of oxygen for use in thebottom zone. Hydrogen sulfide is recovered from the gases exiting thefractionation unit. Sulfur dioxide is recovered from the cobalt oxidedesulfurizing unit during regeneration thereof. The hydrogen sulfide andsulfur dioxide are conveyed to a standard Claus unit for the recovery ofelemental sulfur. The catalyst, having been regenerated by the heatedhot carbon dioxide and oxygen in the bottom zone, and the sand, slag,etc., are recycled through an appropriate lock-bin feed to the top ofthe reactor where it is again mixed with the incoming coalsolventslurry, fresh make-up sand and catalyst feeds.

These and other objects of the invention will become more apparent tothose skilled in the art by reference to the following detaileddescription when viewed in light of the accompanying drawings wherein:

The single FIGURE is a diagrammatic illustration of the process of thisinvention.

Raw, crushed coal is fed via line 10 to a conventional feed lock-bins112 wherein the coal is dried by warm, inert gases such as nitrogenintroduced via line 14. The dried coal is conveyed via line 16 to tank18 wherein it is mixed with oil introduced via line 20 to produce acoal-solvent slurry. A portion of the oil is pressured through line 24by a suitable pump (not shown) and an eductor 26 to draw the coal-oilslurry through line 28 and into line 30 for introduction to the top ofthe reactor tower 32. The reactor tower is a vertically disposedcylindrical vessel, sectioned into three contiguous zones, a top zone34, a middle zone 36 and a bottom zone 38 for various stages ofseparation of liquid and gaseous fuels from the coal introduced to thetop of the reactor.

A hydrocracking catalyst such as cobalt, molybdenum, tungsten, iron orthe like from source 42 is introduced to lock-bin 40, via line 44. Inorder to assist the slurry, and catalyst in flowing downwardly throughhe zones of the reactor tower, sand, metallurgical slag or othersuitable inert particulate material is introduced to the lock-bin 40from the source 46 and line 44. Recycled sand and catalyst is alsointroduced into the lockbin 40 via line 50. The catalyst-sand mixture isintroduced into the top of the reactor 32 via line 52 and is intermixedwith the coal-oil slurry.

The top zone or hydrocracking zone 34 includes alternating convex andconcave baffles 54 and S6 respectively. The baffles 54 are of a suitablemetal material and include an annular collection chamber 58 on theunderside thereof communicated to the upper surface of the baffle 54through a suitable grating or other perforate surface 60. Likewise, eachbaffle 56 is provided with an annular collection chamber 62 which iscommunicated to the upper surface of the baffle through perforatesurface 64. Fluid lines 66 and 68 lead from the collection chamber 58and 62 respectively and are communicated to a manifold line 70 foreventual introduction into a fractionation unit 72 via line 74. Becauseof the dispositions of the alternately convex and concave bafflesforming annular and central openings 63 and 65 respectively, the sand,coal and catalyst mixture flows downwardly through zone 34 in a zig-zagpattern, greatly enhancing liquid, solid and gas contact. Suitablevalves may be placed in the various outlet lines from the annularcollection chambers to regulate the rate of liquid removal. Further, thesand concentration can be increased as required to regulate the speed ofthe downward travel of the mixture thereby controlling the rate ofliquid extraction. Hydrogen is introduced adjacent the bottom of thefirst zone 34 via line 76 for hydrocracking the extracted liquids.

The second zone is in free communication with the first zone andincludes an imperforate conical baffle 78 and an inner cylindricalvessel 80 disposed vertically below the baffle 78. Underlying the vessel80 is a funnel 82 having a spout 84 through which solids from the middleor second zone pass to the third or bottom zone. The inner vessel 80 andthe outer walls of the reactor tower 32 define an annular chamber 86.The baffle 78 is of a smaller diameter than that of the top opening ofthe vessel 80 such that the heavier solids flowing from the top zonewill be permitted to flow into the central chamber 81 of the vessel 80.Air is introduced to the bottom of the annular chamber 86 from asuitable source via lines 90 and 92. Air from the same source isintroduced to the chamber 81 at vertically spaced levels 94 and 96through a series of horizontally disposed nozzles. The air introduced at94 and 96 gasifies the carbonaceous material in the downwardly flowingsolids to producer gas, which flows upwardly through the open end ofvessel 80 to the first zone in a direction countercurrent to thedownward flow of solids. The lighter coal ash is fluidized by theupwardly flowing producer gas and is caused to settle in the annularchamber 86 wherein air introduced via line 92 burns any residual carbonoff of the coal ash. The coal ash is then taken off via line 98 throughsuitable lock bins (not shown) and then to disposal. The top section ofthe middle zone or air gasifier zone contains a fluid bed since the coalash particles are fluidized and forced outwardly to the chamber 86,while the bottom section of the middle zone contains a moving solid bedof sand, catalyst particles and other residual particles.

The sand and catalyst then flows downwardly through funnel 82 and spout84 to the third zone for oxygen and carbon dioxide gasification of anyremaining carbon. The zone includes vertically spaced baffles 100 and102 each having hooded gas pipes 104 permitting the upward flow of gasthrough the moving solid bed and down-flow pipes 106 permitting themoving solid bed to pass through the baffle plates 100 and 102 andeventually out of the reactor tower through lines 108 to lock-bin 110for recycling back to the top of the reactor tower via line 50. Oxygenis introduced in the area between baffle plates 100 and 102 via line112. Carbon dioxide is introduced below the baffle plate 102 via line11.4. Carbon dioxide helps cool the sand prior to its being recycled outthrough line 108. The downwardly flowing solid moving bed will seal thebottom zone from the middle zone against the upward flow of gases atspout 84.

The product carbon monoxide gases are substantially free of nitrogensince only oxygen and carbon dioxide are used to gasify the carbonaceousmaterials. However, the carbon monoxide will contain a substantialamount of sulfur; therefore, it is taken off via line 116 and conveyedto a cobalt oxide desulfurizing unit 118, wherein the cobalt oxide is inits higher oxide form. The sulfur-free carbon monoxide gas exits vialine 120 and is sent to storage.

A certain amount of carbon monoxide is sent to a hydrogen generator 126via line 128 wherein it is reacted with steam injected via line 130 toproduce hydrogen and carbon dioxide. The hydrogen and carbon dioxide arepassed through a carbon dioxide separator 132 with the hydrogen beingsent via line 76 to the first zone in the reactor tower and the carbondioxide being sent to the bottom zone 38 via line 114. Still anotherportion of the carbon monoxide is sent to an oxygen generator 136 vialine 138. The oxygen generator includes at least two cobalt oxide bedsoperating alternately and a vacuum is applied to draw off oxygen vialine 112 for introduction to the third zone 38. The carbon monoxidereacts with part of the oxygen in generator 136 to provide heat requiredfor the endothermic reaction. Air is introduced into the oxygengenerator via line 140 to regenerate the cobalt oxide therein. Thenitrogen from the air stage is taken off via line 142 and a portionthereof may be used for drying the crushed coal in feed lock-bin 12.

The liquids taken from the first zone are introduced to a fractionationunit 72 via line 74. The producer gas from the second zone passesupwardly through the first zone and is taken off via line 73 forintroduction to the bottom of the fractionation unit 72. The resultantfractionation products are taken off via lines 75, 77 and 79 asindicated, while the heavy residual oil is recycled from the bottom ofthe fractionation column via line 20 to the slurry tank 18. Fuel gas istaken from the fractionation unit via line 71 and passed through agasoline absorber 69 and a hydrogen sulfide remover 83. The desulfurizedfuel gas is taken off via line 85 and the hydrogen sulfide is sent vialine 87 to a Claus unit 89.

Air is introduced to the cobalt oxide bed desulfurizing unit 118 vialine 119 to oxidize the cobalt therein back to a higher oxide form afterthe desulfurization cycle, producing sulfur dioxide which is taken offvia line 91 and introduced to the Claus unit 89. Elemental sulfur isrecovered from the hydrogen sulfide and sulfur dioxide and is taken offvia line 93.

It is to be understood that the cobalt oxide beds 118 and 136 comprisedual beds such that, in each unit, while one bed is in a sulfur removalcycle, the other bed may be oxidized or regenerated back to its higheroxide form by the introduction of regenerating air to provide continuousoperation.

The process of this invention will be more fully understood withreference to the following examples:

EXAMPLE I A western coal with the following analysis was extracted witha solvent/coal ratio of 2/1 by weight. The solvent used was a 75 percenttetralin-25 percent decalin solution (by weight).

Coal Analysis (moisture and ash free) Carbon 75.93 per cent Nitrogen1.53 per cent Hydrogen 4.77 per cent Oxygen 16.92 per cent Sulfur 0.83per cent Sand of III weight ratio with coal was used. The coal wasslurried with the solvent and bed into the extractor. The slurry washeated to 700F. prior to injection. Sand was injected into the extractoralong with the slurry. The vessel was maintained at 800F and the coalresidence time was minutes. The liquid stream out of the extractor washydrotreated at 1000 PSIA and 600F and fractionated with the followingweight analysis determined: (after solvent recovery) Gas (mainlymethane) 2.4 percent BTX Gasoline 18.3 percent Light Diesel 26.8 percentHeavy Diesel 46.4 percent Heavy Material for Recycle 6.1 percent Theoverall hydrotreated weight yield of the gas-heavy diesel from coal was63.4 percent based on moisture and ash free coal feed. The unextractedcoal along with the sand was gasified with air to obtain a gas with anet heating value of 230 BTU/SCF. The calculated overall yield ofliquids and gas was 88.3 percent (weight per cent) based on the coalfeed and on a MAF basis.

EXAMPLE ll The same coal of Example I was subjected to the conditions ofExample 1 with the exception that the coal/- solvent ratio was 1/1 byweight. After hydrotreating and fractionation the liquid stream had thefollowing weight composition:

Light Gases (mainly methane) 2.1 percent BTX Gasoline 14.5 percent LightDiesel 22.4 percent Heavy Diesel 52.8 percent Recycle Material (heavy)8.2 percent The liquid and hydrocarbon gas yeild from the coal was 38.1percent based on moisture and ash free basis. The unextracted coal andsand was gasified with air to a gas with a net heating value ofapproximately 242 BTU/SCF. The calculated overall yield of fuel gas andliquids was 89.4- percent based on the carbon feed on a MAF basis.

EXAMPLE III A Southern Illinois coal with the following moisture and ashfree weight analysis was slurried with a solvent consisting of 75percent tetralin percent Decalin (by weight) in a ratio of 2/1 weight tocoal and heated to 500F. prior to entering the extractor.

Carbon 76.7 per cent Nitrogen 1.6 per cent Hydrogen 6.1 per cent Oxygen11.3 per cent Sulfur 4.3 per cent The extractor was maintained at 750Fand the slurry was mixed with an equal weight of sand as the coal sothat the weight ratio of the sand/coal was 1/ 1. The solid residencetime was minutes and then the solids were gasified with air. Theextracted liquids and solvent were hydrotreated at 1000 PSIA and 600F.in excess hydrogen. After fractionation the following weight analysiswas obtained.

Light Hydrocarbon Gases 3.1 percent BTX (gasoline fraction) 19.2 percentLight Diesel Fraction 32.5 percent Heavy Diesel Fraction 36.8 percentRecycle Fraction (bottoms) 8.4 percent The hydrotreated yield (weight)of the MAF coal was 68.4 percent based on the total MAF coal charge(excluding the hydrogen required for hydrotreating). The solids weregasified with air to a fuel gas of approximately BTU/SCF. The overallyield of the liquids and gas based on the MAF feed was 89.2 per cent.

EXAMPLE IV The same type of coal as in Example 111 was extracted underthe same conditions as in Example 111 with a solvent/coal weight ratioof 1/1. After fractionation the weight analysis gave:

Light Gas (hydrocarbon) Fraction 2.8 percent BTX (gasoline fraction)18.4 percent Light Diesel Fraction 35.7 percent Heavy Diesel Fraction33.9 percent Bottoms (recycle) Fraction 9.2 percent The solids weregasified with air to a gas with a heating value of approximately BTU/SCFand the overall yield (weight percent) was 90.1 percent based on the MAFcoal feed. The hydrotreated fraction yield was 41.2 percent (weight)based on the MAF coal feed.

EXAMPLE V The same type of coal as in Examples 111 and IV was heated inthe extractor with no solvent and the extracted liquids afterhydrotreating gave the following weight analysis:

Light Hydrocarbon Gas Fraction 2.3 percent BTX (gasoline fraction) 10.4percent Light Diesel Fraction 34.2 percent Heavy Diesel Fraction 42.7percent Bottoms (recycle) Fraction 10.4 percent The above hydrotreatedfractions amounted to 21.4 percent of the coal MAF charged. The solidswere gasified with air to give a gas having a heating value of BTU/SCF.The overall yield (weight) of the liquids and fuel gas was 91.3 percentbased on the MAF coal feed.

In a general manner, while there has been disclosed an effective andefficient embodiment of the invention, it should be well understood thatthe invention is not limited to such an embodiment as there might bechanges made in the arrangement, disposition, and form of the partswithout departing from the principle of the present invention ascomprehended within the scope of the accompanying claims.

We claim:

1. A method of simultaneously recovering fuel liquids and gases fromcoal comprising the steps of fonning a slurry of crushed coal and oil,mixing the slurry with a catalyst and introducing said mixture to thetop of a vertical reactor tower, dividing said tower into top, middleand bottom contiguous zones and passing said mixture continuouslythrough said zones whereby liquids are extracted and taken off in saidtop zone, the carbon in said mixture is gasified in said middle zonewith air, and any remaining carbon is gasified with oxygen and carbondioxide to carbon monoxide in said bottom zone.

2. The method of claim 1 including the step of separating coal ash fromsaid mixture in said middle zone by fluidizing said ash from saidmixture.

3. The method of claim 1 including the step of introducing an inert,solid particulate material into said mixand desulfurizing it by reactingthe sulfur therein with cobalt oxide in its higher oxide form to formcobalt sulfide.

6. The method of claim 3 wherein said mixture follows a tortuous paththrough said top zone.

2. The method of claim 1 including the step of separating coal ash fromsaid mixture in said middle zone by fluidizing said ash from saidmixture.
 3. The method of claim 1 including the step of introducing aninert, solid particulate material into said mixture to serve as aconveying medium for said slurry and catalyst through said zones.
 4. Themethod of claim 3 wherein said sand and catalyst are taken from saidbottom zone and recycled to said top zone.
 5. The method of claim 1including the steps of removing said carbon monoxide from said bottomzone and desulfurizing it by reacting the sulfur therein with cobaltoxide in its higher oxide form to form cobalt sulfide.
 6. The method ofclaim 3 wherein said mixture follows a tortuous path through said topzone.